In yarn handling machines such as spinning frames, twisters or the like, textile carriers or bobbins are received over rotatable spindles along the length of the machine. While on the spindles, a package of yarn is built along the carrier after which the carrier is removed from the machine and an empty carrier substituted therefor. The particular building of the yarn package is determined by a unit called a builder motion which causes an element of the machine to move in a vertical plane along said carrier while yarn is deposited on the carrier at the juncture of same with the traversing element. Particular package design is thus very versatile, but always ends up in wrapping yarn along the majority of the length of the carrier, generally in a precise fashion. Regardless of the particular builder motion, once the package has been completed, it becomes desirable, if not necessary, to adjust the machine to permit proper removal of the full yarn carriers therefrom.
Historically, "bearing down" as the adjustment is referred to has constituted a manual operation where a foot lever was provided under the frame and was stepped on by the operator. The operator's weight then overcame a counter weight and forced a ring rail, etc. downwardly to a point adjacent the bottom of the yarn package for easy removal of the package from the spindle. Obvious problems have existed with manual bear down systems. They are difficult for all operators, but are near impossible to operate by some of the female operators who are not heavy enough or strong enough to apply the needed force. Textile companies were thus forced to use male operators. Automatic bear down systems were then added to the frames. These automatic systems have generally afforded a force of some type against a portion of the traverse apparatus to directly or indirectly cause the traverse element, normally the spinning rail, to be moved downwardly, adjacent the base of the spindle. Electromechanical, mechanical, hydraulic, pneumatic and other type systems have heretofore been utilized to provide the necessary bear down force.
Even with the automatic bear down systems, certain problems have continued to exist to prevent truly successful operation of the units. For example, a constant bear down, depending upon the type of rate of speed, has been quite elusive. In a pneumatic or hydraulic system, an initial lag exists after which a gradual build-up of power is produced with the graduated force applied. Further, since yarn is continually wound around the carrier during the period when the bearing down occurs, varying amounts of yarn are wound around the carrier, unless a constant rate is available. Unwinding of the yarn from the package is very important to success of the overall operation. Hence, it is important to provide a constant speed bear down system to realize winding of a constant amount of yarn around the carrier during bear down which can be easily removed from same. Moreover, once the rail is in the down position, it is customary to permit continued operation of the frame for a short period of time to permit the several additional wraps of yarn for production of a transfer tail. Transfer tails permit the proper thread-up of the yarn at subsequent operations and consistency of the transfer tail length adds to quality control and overall efficiency in general.
Mechanical bear down systems have been utilized in the past where a plurality of gears were employed in a very complex arrangement such that the mechanical approach has been considered impractical. As pointed out above, hydraulic and pneumatic systems have also encountered difficulty due to leaks and the like. Such problems led not only to possible malfunctions, but also to unsightly conditions surrounding the machinery, which are bad because of both aesthetic considerations and certain sightly hazards.
The present invention provides a bear down system that circumvents problems of the prior art. With the present system, a constant rate of bear down speed is realized, with the rate being variable. Secondly, the present system is automatic, and when coupled with the constant rate of speed, permits the attainment of a uniform yarn package. Furthermore, the present system may also be manually operated, if desired, which permits adjustment of the frame to facilitate convenience of spindle plumbing, changing of yarn travellers, machine maintenance, and the like.